Many electronic devices, such as tablet computers, electronic book readers, smartphones, and other mobile computing devices, include an ambient light sensor (ALS). An ALS measures the surrounding ambient light, and based on such measurements, the brightness or light intensity of luminance components are adjusted. Such luminance components include a graphical display, an indicator light, a backlit button, and the like. For example, if an electronic device is used outdoors on a sunny day, the graphical display's brightness may be automatically adjusted to a maximum setting. For further example, if an electronic device is used in a dark room at night, the graphical display's brightness may be automatically adjusted to a minimum setting.
An ALS may have one or more photodiodes, or the like, and each photodiode may measure the light intensity or lux of various ranges of wavelengths of ambient light. Due to manufacturing variances between sensors, for example part-to-part variations, each ALS may provide different measurements of the same ambient light conditions. An ALS may also be positioned behind a glass, such as a cover glass, and in order to camouflage or hide the ALS from the view of a user, the portion of the cover glass covering the ALS may be darkened, colored, or blackened. Because darkened glass can absorb visible light, darkened glass can reduce the transmission of light in the visible light spectrum, such as green light, but not significantly reduce the transmission of light in the invisible light spectrum, such as infrared light. Due to variances in each cover glass's transmission of ambient light to an ALS, such as when one cover glass is slightly darker than another cover glass, there may be variances in light measurements of the same ambient light conditions by sensors behind different darkened glass.